Abstracts

Rationale: Many patients with epilepsy use antiepileptic drugs (AEDs) in combination. The incidence of psychiatric disorders in patients with epilepsy is higher than in the general population, and the elderly in general often use polypharmacy, increasing the total drug load of CNS-active drugs. The purpose of this study was to study polypharmacy aspects in elderly vs younger patients with epilepsy.Methods: The data consisted of all prescriptions of AEDs from the Norwegian Prescription Database (NorPD). A 3-month period (September to November 2012) was used to elucidate the extent of polypharmacy. Variables included anonymous data regarding age, gender, reimbursement codes for specific diagnoses and utilization of AEDs (N03A) and psychotropic drugs (N05A and N06A). Elderly patients were defined as those 60 years and above and younger patients between 0-59 years. The National Institute of Public Health approved the study.Results: The proportion of elderly patients with epilepsy using polypharmacy (2-9 CNS-active drugs) was 21% (n=9553), versus 18% (n=21306) in younger patients. The enzyme inducers (phenobarbital, phenytoin and carbamazepine) were 2.8 times more frequently used in polypharmacy in the elderly (n=375), as compared to younger patients (n=290). The most commonly used psychotropic drugs used in combination with AEDs in younger/elderly patients were olanzapine (n=164/65), quetiapine (n=131/34) and amitriptyline (n=89/50). Selective reuptake inhibitors (SSRIs) were used in combination with AEDs in only 0.4 % of elderly (n=37) and younger patients (n=81). The use of lamotrigine in combination with other AEDs (carbamazepine and valproic acid) and quetiapine was 3.3 and 2.5 times higher in younger than in elderly patients, respectively.Conclusions: The extent of polypharmacy in both elderly and younger patients is reflected by concomitant use of up to nine CNS-active drugs. The most frequent combinations in the elderly include enzyme-inducing AEDs. In younger patients lamotrigine is commonly used and may be affected by comedication. A heavy drug load may cause excessive adverse effects and toxicity. Awareness of potential pharmacokinetic drug interactions and routine therapeutic drug monitoring, as well as careful clinical consideration, is of great importance.